1. Field of the Invention
This invention relates to a method for the production of a halogen-containing aromatic compound useful as a raw material for resins which excel in heat resistance, chemical resistance and water repellency, and have a low dielectric and a low refractivity.
This invention further relates to a novel halogen-containing naphthalene compound useful as a raw material for resins which have a high glass transition temperature and excel in chemical resistance, water repellency, and low refractivity.
2. Description of the Related Art
It has been heretofore known that halogen-containing aromatic compounds, particularly those halogen-containing aromatic compounds which incorporate a difluoroalkyl group or a bromodifluoroalkyl group therein, are useful as raw materials for resins which excel in heat resistance, chemical resistance and water repellency, and have a low dielectric and a low refractivity. Among other halogen-containing aromatic compounds, particularly xcex1,xcex1xe2x80x2-dibromo-xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetrafluoro-p-xylene is known as constituting itself a raw material for per-xcex1-fluoro[2,2]paracyclophane which is a precursor for poly(xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetrafluoro-p-xylene). For example, Journal of Organic Chemistry, Vol. 62, pp. 7500-7502, 1997 has stated that per-xcex1-fluoro[2,2]para-cyclophane derived from a halogen-containing aromatic compound can be used as a precursor for poly(xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetrafluoro-p-xylene) (referred to simply as xe2x80x9cParylene Fxe2x80x9d in the present specification) and that the Parylene F resulting from the polymerization thereof possesses a low dielectric constant and can be used an interlayer insulating film for semiconductors of the next generation. As means for the production of such a halogen-containing aromatic compound, a method which comprises irradiating an aromatic compound incorporating therein a CX2H group (wherein X represents F or Cl) with an UV light while using bromine (Br2) as a brominating agent (Zhurnal Organicheskoi Khimii, 1993, 29, 1999) and a method which comprises effecting the irradiation with light while using N-bromosuccinimide as a brominating agent (Zhurnal Organicheskoi Khimii, 1993, 29, 1999; J. Org. Chem., 1993, 58, 1827-1830) have been known.
The former method which uses bromine (Br2) as a brominating agent, however, has the problem of obtaining the target compound only in a low yield (27 to 30%). Then, the target method which uses N-bromosuccinimide as a brominating agent, although indeed enables the relevant reaction to proceed efficiently, it still entails the problem of suffering succinimide to accumulate on the side of light incidence of the reaction vessel made of glass with the progress of the reaction and eventually impede the progress of this reaction and the problem of using N-bromosuccinimide, an expensive raw material, and consequently suffering the target product obtained by such a method to become inevitably expensive. Thus, none of the known methods is capable of producing a halogen-containing aromatic compound inexpensively in a high yield.
The semiconductor technology represents the existing forefront techniques for fine fabrication and mass production. The technology for the production of semiconductors culminates in the technique for fine fabrication and the technique for high density packaging. It has promoted the advance of semiconductors toward higher integration, greater addition to function, higher reliability, and lower cost. The formation in particular of a multilayer wiring which has emerged from the growth of high integration dictates fulfillment of such requirements as ample heat resistance, high electric insulation, low dielectric constant, high chemical and mechanical stability, and easy fine fabrication.
Since the Parylene F excels in insulation and yet possesses only such low thermal stability as 450xc2x0 C., it fits only limited applications on account of insufficient heat resistance when higher heat resistance is required as, for example, in the process for the production of semiconductors. Various organic high polymers which are aimed at exalting ability of fabrication and facilitating impartation of varying properties have been developed and already adopted for actual use in numerous fields. It is, therefore, proper to conclude that the desirability of developing a resin excelling in heat resistance or a raw material for such a resin is rated very high.
An object of this invention, therefore, is to provide a method for producing a halogen-containing aromatic compound, particularly a halogen-containing aromatic compound incorporating a bromodifluoroalkyl group, inexpensively in a high yield.
Another object of this invention is to provide a halogen-containing naphthalene compound which is useful as a raw material for a resin which excels in heat resistance, chemical resistance and water repellency, have a low dielectric constant and a low refractivity.
The present inventors, while pursuing a study on the production of an aromatic compound (II) incorporating therein a (CH2)nCX2Br group by the reaction of photo-bromination of an aromatic compound (I) incorporating therein a (CH2)nCX2H group (wherein X represents a fluorine or chlorine atom and the X""s may be same or different, and n is an integer in the range of 0 to 4) with a brominating agent, have found that the aromatic compound (II) aimed at can be obtained in a high yield by performing the reaction of photo-bromination by continuing removal of hydrogen bromide generated in the reaction system; and/or in an atmosphere of a low oxygen content by removing oxygen present in the reaction system prior to the reaction and/or continuing removal of oxygen during the course of the reaction; and optionally by combining the above step(s) suitably with a step of irradiating the reaction system with a light from a fluorescent lamp as a light source.
On the basis of the knowledge that the Parylene F can be produced by a process which comprises the steps of reduction, dimerization, cyclization, and etc. of 1,4-bis(bromodifluoro)benzene, the present inventors have selected various compounds in place of the 1,4-bis(bromodifluoro)benzene and measured glass transition temperatures of these compounds, to find that a halogen-containing naphthalene compound using a naphthalene ring in place of the benzene ring possesses characteristic properties ideal for this compound to be used as a raw material of a resin excelling in the property of glass transition temperature.
The present invention has been perfected based on this knowledge.
The objects mentioned above can be accomplished by a method for the production of an aromatic compound (II) having a (CH2)nCX2Br group (wherein X represents a fluorine or chlorine atom and the X""s may be same or different, and n is an integer in the range of 0 to 4) by the reaction of photo-bromination of an aromatic compound (I) having a (CH2)nCX2H group (wherein X and n are as defined above) with a brominating agent, wherein the photo-bromination reaction is carried out while removing hydrogen bromide generated in the reaction system and/or in an atmosphere of a low oxygen content.
Further, the other object mentioned above can be accomplished by a halogen-containing naphthalene compound represented by the following formula (1): 
wherein Y represents xe2x80x94CF2H, xe2x80x94CF2Br, or xe2x80x94CHO group, Z1 and Z2 independently represent a halogen atom, and p and q independently are an integer in the range of 0 to 3.
The method of this invention permits a halogen-containing aromatic compound, particularly a halogen-containing aromatic compound incorporating therein a bromodifluoroalkyl group, which is useful as a raw material for a resin excelling in heat resistance, chemical resistance and water repellency, and having a low dielectric constant and a low refractivity to be produced inexpensively in a high yield. In the process for the production of the halogen-containing aromatic compound (II) by the reaction of photo-bromination, by performing the reaction of photo-bromination in particular i) by continuing removal of hydrogen bromide generated in the reaction system; and/or ii) in an atmosphere of a low oxygen content particularly by removing oxygen present in the reaction system prior to the reaction and/or continuing removal of oxygen during the course of the reaction; and optionally iii) by combining the above step(s) suitably with the step of irradiating the reaction system with a light from a fluorescent lamp as a light source, the aromatic compound (II) aimed at can be obtained in a high yield. Further, since the aromatic compound (II) can be obtained in a high yield, the purification of the product can be facilitated and the cost of production can be repressed.
According to this invention, a novel halogen-containing naphthalene compound can be provided. The halogen-containing naphthalene compound of this invention is useful as a raw material for a resin which excels in heat resistance, chemical resistance and water repellency, and has a low dielectric constant and a low refractivity.